1. Field of the Invention
The present invention relates generally to methods and compositions for stimulating and maintaining enhanced growth in plants. More particularly, the present invention relates to plant growth formulations which contain methanol, methanol metabolites and/or amino acids, which compositions are able to increase turgor pressure and enhance carbon fixation in plants.
Photosynthesis is the process by which photosynthetic plants utilize solar energy to build carbohydrates and other organic molecules from carbon dioxide and water. The conversion of carbon dioxide to such organic molecules is generally referred to as carbon fixation and, in most plants, occurs by the reductive pentose phosphate cycle, usually referred to as the C.sub.3 cycle. The C.sub.3 cycle involves the carboxylation of ribulose diphosphate (RuDP) with carbon dioxide to produce hexoses and other organic molecules.
Fertilizers for higher plants generally include nitrogen, phosphorus, and potassium, which are referred to as primary nutrients or macronutrients. Fertilizers often further include certain secondary nutrients, such as iron, sulfur, calcium, and magnesium, as well as various minerals and micronutrients. Heretofore, little attention has been paid to providing fertilizers which act directly to enhance carbon fixation in higher plants. Conventional fertilizer formulations have generally been directed at the delivery of the recognized primary, secondary, and micronutrients, but have usually not included a carbon source and in particular have not included a carbon source intended to enhance carbon fixation by the C.sub.3 cycle or otherwise.
For these reasons, it would be desirable to provide improved methods and formulations for promoting plant growth by enhancing the rate of carbon fixation within the plant. It would be particularly desirable if such methods and compositions were effective with most or all higher plants, more particularly including those plants which fix carbon via the C.sub.3 pathway. The present invention should further provide convenient methods for applying the compositions, such as applying the compositions as a foliar spray, and should preferably result in increased plant turgidity. Additionally, it would be desirable if the methods and compositions of the present invention could promote rapid growth and maturing of the treated plant, increase sugar content in the plant, reduce the watering requirement of the plant, and enhance environmental tolerance of the plant.
2. Description of the Background Art
Study of the path of carbon in photosynthesis four decades ago (A. A. Benson (1951), "Identification of Ribulose in C.sup.14 O.sub.2 Photosynthesis Products" J. Am. Chem. Soc. 73:2971; J. R. Quayle et al. (1954), "Enzymatic Carboxylation of Ribulose Diphosphate" J. Am. Chem. Soc. 76:3610) revealed the nature of the carbon dioxide fixation process in plants. The metabolism of one-carbon compounds other than carbon dioxide had been examined, and methanol was found to be utilized by algal strains of Chlorella and Scenedesmus for sugar and amino acid production as rapidly as is carbon dioxide. Since both types of early experiments were performed with substrate on a tracer scale, it was neither clear that the rates were comparable nor what the pathway for methanol conversion to sucrose involved. A subsequent publication on the subject (E. A. Cossins (1964), "The Utilization of Carbon-1 Compounds by Plants" Canadian. J. Biochem. 42:1793) reported that plants metabolize methanol to carbon dioxide, glycerate, serine, methionine, and other sugar or structural precursors rapidly. The conclusion that methanol is readily oxidized to formaldehyde and converted to fructose-6-phosphate has been reported in bacteria (C. L. Cooney and D. W. Levine (1972), "Microbial Utilization of Methanol" Adv. Appl. Microbiol. 15:337) and fungi (W. Harder et al. (1973), "Methanol Assimilation by Hyphomicrobium sp." J. Gen. Microbiol. 78:155). Based on these studies of microorganisms it was concluded that formaldehyde condenses with pentose-5-phosphate to yield allulose-6-phosphate which epimerizes to fructose-6-phosphate.
Methanol and other alcohols have been included in certain prior fertilizer formulations for various purposes. U.S. Pat. No. 3,918,952, discloses the incorporation of 1-15 parts by volume lower alcohol in clear liquid fertilizers as stability enhancers. U.S. Pat. No. 4,033,745, discloses the incorporation of 0.05% to 1% alcohol in liquid fertilizers as a stability enhancer. U.S. Pat. Nos. 4,409,015 and 4,576,626 describe the addition of alcohols to fertilizers to enhance solubilization of phospholipids. See also Hungarian patent abstract T45468 and USSR patent abstract 84-3794472, which describes the incorporation of methanol into fertilizers at unspecified concentrations.
British patent application 2 185 472 A describes foliar plant feeding compositions which comprise from 2% to 4% by weight of protein hydrosylate including amino acids, polypeptides, and oligopeptides. Particular amino acids are not identified. The application of oxamide (H.sub.2 N--CO--CO--NH.sub.2) in foliar sprays to wheat and soybean as a slow-release of nitrogen source is described in Schuler and Paulsen (1988) J. Plant Nutr. 11:217-233. The foliar application of radiolabelled proline to wheat is described in Pavlova and Kudrev (1986) Dolk. Bolg. Akad. Nauk. 39:101-103. Barel and Black (1979) Agron. J. 71:21-24 describes foliar fertilizers incorporating polyphosphate compounds combined with a surfactant (0.1% Tween.RTM. 80). Chinese patent publication 1046886A describes plant leaf fertilizers including amino acids. U.S. Pat. No. 4,863,506, describes the incorporation of L-(d)-lactic acid in foliar sprays where the lactic acid is alleged to act as a growth regulator.
A portion of the experimental section presented in this application was published in Nonomura and Benson (1992) Proc. of the Natl. Acad. of Sci. USA 89:9794-9798. This publication occurred prior to the filing date of the patent application Ser. No. 07/901,366.